This invention relates to a chamfering apparatus for commutators in general, and more particularly to such an apparatus for the maintenance of commutators of DC traction motors mounted on electric cars and/or electric locomotives.
Referring to FIGS. 1 to 3, part of a DC motor commutator is shown which includes commutator segments 1 and mica segments 2 which insulate the adjacent commutator segments 1 from each other. These segments 1 and 2 are disposed alternately around the circumference of a rotor shaft (not shown) and are fixed in place by clamps 3 and spiders 4. As illustrated in FIG. 3, the tops of the mica segments 2 are generally positioned lower than the tops of the commutator segments 1 by a distance "h", and the edges of the commutator segments are chamfered as shown by "c". Generally, commutator segments are chamfered manually using hand tools, or mechanically using special equipment, i.e., a chamfering apparatus for commutators.
FIGS. 4 and 5 illustrate a conventional chamfering apparatus, wherein a commutator assembly 11 is mounted on an armature 10 having a shaft 12. The opposite ends of the armature shaft 12 are supported by a chuck 20 and a rotary spindle 24 in the manner of a machining lathe. A clamping device 21 prevents the armature shaft from shifting laterally. The chuck 20 is secured to a support table 14. An indexing cylinder 17 indexes slots on the commutator assembly by rotating the chuck unit a predetermined amount through a reduction unit 16, transmission gears 18 and a clutch 19.
The indexing cylinder 17 is fixed to the support table 14 which is slidably mounted on a bed 13 and moved, by means of a handle 15, to adjust its position according to the length of the armature 10 to be machined. The spindle 24 is fixed to a tailstock 22 which is moved back and forth by means of a cylinder 23. A cutter bit holder 25 and an indexing stop 26 are fixed to a support table 27 which is mounted on a base 28 adjoining the bed 13. In operation, the ends of the armature shaft 12 are mounted between the chuck 20 and the spindle 24, and then the relative distance between the commutator assembly 11 and the cutter bit holder 25 is adjusted. The armature 10 is then rotated by the operation of the indexing cylinder 17, and is stopped at the positions that have been determined by the indexing stop 26.
After this indexing operation, the commutator segments are chamfered by the reciprocating movement of the cutter bit holder 25 parallel to the slots of the commutator assembly 11. This operation is repeated continuously from one segment to another, and is stopped automatically after the chamfering of all of the segments has been completed.
In such a conventional apparatus there are several disadvantages. In preparation for the chamfering operation it is necessary to remove the traction motors from the vehicle trucks, and then disassemble the motors to extract the armatures. After the chamfering operation, the reverse procedures have to be carried out. The size of the chamfering apparatus is also large because it must accommodate the installation of the entire armature body. Furthermore, it requires at least two drive devices, such as the cylinders 17 and 23, for both indexing and chamfering.